Publication Date

10-16-2013

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Raptor Biology

Department

Biology

Supervisory Committee Chair

Julie A. Heath

Supervisory Committee Member

James R. Belthoff

Supervisory Committee Member

Jesse R. Barber

Abstract

Early exposure to stressors affects subsequent stress responses in both mammalian and avian species, with the likelihood for lasting effects depending, in part, on the magnitude of the stressor. However, it is unclear whether lasting effects are the result of developmental changes to the hypothalamic-pituitary-adrenal (HPA) axis or habituation to the stressor. I investigated the effects of human handling, a known stressor, in free-living American kestrel (Falco sparverius) nestlings to determine if this brief, non-invasive stressor causes lasting changes in the stress response of handled birds, and whether alterations in the stress response were the result of developmental changes (early-handled birds) or habituation (later-handled birds). Broods were randomly assigned to one of three treatment groups: 1) early-handled nestlings were held daily for 15 min for 7 days following hatching, 2) late-handled nestlings were held for the same time and duration beginning on the 18th day post-hatching, and 3) control birds were not handled before sampling for circulating corticosterone (CORT). When nestlings were 25 or 26 days old, they were exposed to either a handling restraint protocol (similar to the treatment of handling) or a novel noise stressor. The stress test not applied on the first day was conducted the next day. During the hour-long restraint protocol, I collected five 75 ul samples of blood through venipuncture of the alar vein. HPA response to a novel stressor was measured by sampling CORT immediately after exposing birds to 10 min of 96 dB(A) (±1 dB) white noise. I analyzed serum CORT levels using enzyme-linked immunoabsorbent assays (ELISA). There was no effect of handling treatment on CORT patterns sampled over the 1 hr restraint test (P = 0.092), though a priori contrasts showed a significant difference between CORT levels of late-handled and control birds at 60 min (P = 0.01). Late-handled birds had lower CORT compared to control birds. In addition, there was no significant differences among handling treatments on noise-induced CORT (P = 0.94). Taken together, these results suggest that the HPA axis was unaffected by human handling and that the changes in CORT at 60 min in late-handled birds is likely the result of habituation to human handling rather than to developmental changes. Further, results indicate that mild and brief stress associated with human handling is unlikely to have negative lasting effects on the stress physiology of young birds.

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